Scientists use 3D printing to develop 4D materials to make molecular machines

Recently, Dr. Chenfeng Ke of Dartmouth College in the United States and his lab developed a kind of super smart material with rotaxanes and made use of 3D printing technology to make it a nano-scale polymer lattice cube. This 4D material can lift 15 times its own weight of the object, the application of broad prospects.

Rotamanes are dumbbell-shaped molecules that convert the input energy in the form of light, heat, etc. into molecular motion. In other words, they respond to external stimuli. They are also called nanomachines.

Dr. Chenfeng Ke of Dartmouth College in the United States and his lab developed a kind of super smart material with rotaxanes. By 3D printing these nanoscale molecules, they created a nanocrystalline polymer lattice cube that can lift 15 times its own weight, which equates to a person lifting a car.

"Our design is based on a widely researched molecular family of polyrotaxanes," explains Dr. Ke, "They have multiple rings on one molecular axis and in our new material these rings are rings Like sugar, while the molecular axis is a polymer. If we provide an external stimulus, such as water, these rings, which are optionally shuttling back and forth, can be glued together to form a tubular array. When this occurs, the molecular stiffness Will be changed, just like a lot of sliding beads are worn on a rope, making the rope sturdy like a pole. "

Dr. Ke and his team's goal is to build a polymer from billions of molecules that bind water. The difficulty with allowing rotaxanes to work, he said, is that when the nanorods are randomly oriented, their ring motions cancel each other out, rendering them useless macroscopically. However, 3D printing enables researchers to control their movements.

"By integrating 3D printing technology, we can transform the random shuttle motion of these nanoscale loops into smart materials that work on a macroscale scale," Dr. Ke continued, explaining that "aligning molecules in the right direction amplifies their movement When we add water, the polyrotaxane rings are held together by hydrogen bonds, and the tube arrays are then stacked together in a more orderly manner. "

"When they were in this configuration, molecular coordination became easier, and on this basis we successfully printed the lattice-like 3D structure."

Once the structure is printed, Dr. Ke's team solidifies them and lets them work. These 3D printed cubes are easy to deform and rebuild due to their hollow lattice construction. By using a solvent as a catalyst, the team is free to switch the movement of the molecular ring structure from shuttle to quiescence and back to the shuttle. The layman's argument is that by adding and removing a solvent, they allow the cube to expand, lifting an object and then restoring the cube to its original shape.

Researchers used this 3D printed cube to lift a small, 1.6-mm coin, which sounds trivial but Ke said it is a big step forward in making the nanomachine work macroscopically.

"We want scientists to use this 3D printed cube to further develop smart materials and devices," he concluded. "These molecular machines can be used as flexible robots to perform, for example, by adding shrinkage and distortion to this ascending motion A complex task similar to that done by humans. "